Injury to the Head--_Concussion of the Brain._--The symptoms are very similar to those of shock, with unconsciousness, but it may be possible to rouse the person. The pupils are equal and dilated or contracted, and react sluggishly to light. The breathing is shallow and slow with sighing, the pulse feeble. The muscles are relaxed but not paralysed. Vomiting and involuntary micturition and defæcation may occur. The temperature is usually subnormal. Cerebral Compression.--This, when due to injury, is usually associated with fracture of the skull and hæmorrhage. Insensibility is complete, the person cannot be roused. The pupils may be unequal, contracted or dilated, and may not react to light. The breathing is slow, stertorous, and may be irregular, or Cheyne-Stokes in type. The pulse is full and bounding, the cheeks are blown out during expiration. Paralysis, rigidity, or convulsions may be present on one side of the body. There may be retention of urine, with overflow incontinence. In cases associated with severe fracture or hæmorrhage within the skull, the conjunctivæ may be chemosed, or there may be hæmorrhage from the nose or ear; and a flow of cerebro-spinal fluid may take place from the nose. Alcohol.--In coma due to alcohol, there will be an alcoholic odour of the breath, alcohol in the stomach contents, and it can be detected in the urine. The odour of alcohol in the breath may be due to the administration of alcohol by an outsider at the onset of the symptoms which have ended in the coma. The pupils are equal, contracted, the conjunctival reflex present, and the pupil dilates on pinching the skin of the neck. The pulse is rapid, at first strong it becomes feeble, the respirations snoring. If the coma be not complete, muscular inco-ordination may be noticed. The person can usually be aroused by stimulation. In pure alcoholic coma the presence of the special features of coma from other causes will be absent. It must be remembered, however, that alcoholic coma may be combined with other kinds, and the more serious form should be kept in mind. Where there is the slightest doubt in the diagnosis, one‘s procedure should be ruled by the possibility of the graver cause. Opium or Narcotic Poisoning.--The skin is usually perspiring freely, moist and cold; the countenance placid, pale and ghastly, the lips livid. The eyes are heavy, and the pupils contracted to a pin-head and equal, the conjunctival reflex usually present. There is the odour of opium in the breath. The pulse is slow, and the respiration stertorous and slow. There is no paralysis, and the person can be momentarily roused by a sharp question or blow. Apoplexy.--The person is with difficulty, if ever, temporarily aroused. The face is red and bloated. Respiration suspirious and stertorous, and there is often Cheyne-Stokes breathing. The pupils are dilated or irregular; in pontine hæmorrhage, contracted. The temperature may at first be subnormal but gradually rises.